Machine for hot dimpling



Nov. 27, 1956 a v. CHRISTENSEN 2,771,931

MACHINE FOR HOT DIMPLING Filed April 29, 1953 7 Sheets-Shani i 70 l e \i' 1 s9 426 b as 'g 680 g I 68 I3 420 g9 go s i o I INVENTOR.

Eowm V. CHRISTENSEN Agent Nov. 27, 1956 E. v. CHRISTENSEN 2,771,931

MACHINE FOR HOT DIMPLING Filed April 29, 1955 'Y Shee ts-Sheet 2 INVENTOR. EDWIN V. CHRISTENSEN Nov. 27, 195-6 E.V,, CHRISTENSEN 1,

MAcHfNE FOR-HOT DIMPLING Filed April 29, 1953 7 'rsheets-slhut s 'iuml "I" IN V EN TOR.

; i J 36 EDWIN V CHRISTENSEN gem Nov. 27, 1956 ...v. CHRISTENSEN 2,771,931

MACHINE FOR HOT DIMPLING Filed April 29, 195;:v 7 Sheets-Sha e; 4

INVENTOR. EDWIN V. CHRISTENSEN NOV. 7, 1956 E.. \f-.'CHRISTENSEN 2771,93 1

MACHINE FOR HOT DIMPLING Filed April 2Q, 1953 7 sheets-shut .5

use 66 C) O 62 F E- 4| 5 l 52 go ,u: 3R

443 1 49 5| Fig. 11

442 v 4? 414 u g r i 50 404 ms w I5 INVENTOR.

/ EDWIN V CHRISTENSEN Agen 7 Sheets-Sheets Filed April 29,- 1953 INVENTOR. EDWIN V. CHRISTENSEN 1956 E. v. CHRISTENSEN 2,771,931

MACHINE FOR HOT DIHPLING Filed 5 :11 29, 155:5. '7-'S1ia'ets- Shaet 7 Fla- INVENTOR. EDWIN V. CHRISTENSEN AgeN'r United States atent MACHINE FOR HOT DIMPLING Edwin V. Christensen, Hollywood, Calif., assignor to Lockheed Aircraft Corporation, Burbank, Calif.

Application April 29, 1953, Serial No. 352,002

14 Claims. (Cl. 153-21) This invention relates to the dimpling and riveting of sheet metal and relates more particularly to means for hot dimpling sheet metal parts and the like.

Certain high strength aluminum and magnesium alloys employed in the construction of aircraft, and the like, often crack when dimples are formed or pressed therein to receive flush rivets. Such cracking at the dimples renders the parts unusable and they must be discarded. There are methods for preheating the metal in the areas to be dimpled which have been proposed and used to avoid this cracking. One of the earlier methods involved the heating of the dimpling tools themselves but such heating damages the tools and provides inadequate heating of the area to be dimpled because the tools present complementary conical surfaces so that the punch initially makes contact with the work at only its apex or tip region while the female anvil has only peripheral contact at the other side of the work. When two or more sheets are to be simultaneously dimpled it is, of course, more difiicult to properly heat both sheets by merely heating the dimpling tools. Another method that has heretofore been employed utilizes annular heaters surrounding the dimpling tools requiring that the heat from the heaters flow inwardly through the metal of the sheets into the areas to be actually dimpled and in order to bring these areas to the required temperature to avoid cracking, the surrounding areas of the work must be raised to excessively high temperatures. Furthermore, in such prior hot dimpling machines the rivet holes have been prepunched to constitute pilots for locating the dimpling tools. The preformed holes not only constitute weak areas at the centers of the dimples but the dimpling operation alters the openings so that the riveting operations require additional or excessive upsetting of the rivets in order to fully occupy the holes.

It is a general object of this invention to provide a simple, practical and dependable means for hot dimpling the work in a manner to avoid cracking thereof.

Another object of the invention is to provide a machine of this character that operates to effectively and expeditiously heat the exact area of the work to be dimpled in such a manner that the dimple may be formed therein immediately subsequent to the heating thereof. In the machine of this invention there is no necessity to excessively heat the region of the work around the area to be dimpled and there is little or no delay incident to the heating operation.

Another object of the invention is to provide an improved hot dimpling machine operable to pre-heat and dimple superimposed layers of sheet metal or material prior to forming the hole in the center of the dimple, the heating of the area to be dimpled being elfected under pressure to assure intimate contact between the work and the heaters and the eflicient flow of heat through the several layers of material. The machine includes heating units at the opposite surfaces of the work and maintains the surfaces of the work and units in pressure contact during the heating cycle.

2,771,931 Patented Nov. 2?, 1956 It is a further object of the invention to provide a hot dimpling and riveting machine of this kind wherein the work or material is heated as one phase or step of a complete automatic riveting cycle involving the heating, dimpling, punching and riveting all in a predetermined sequence.

Other objectives and features of the invention will become apparent from the following detailed description of a typical preferred form and application of the invention wherein:

Figure 1 is a side elevation of the principal portion of a machine embodying the invention with certain parts appearing in vertical cross section;

Figure 2 is an enlarged view taken substantially as indicated by line 22 on Figure 1 with certain parts appearing in vertical cross section;

Figure 3 is a horizontal sectional view taken as indi cated by line 3-3 on Figure 2;

Figure 4 is an enlarged front elevation of the upper heating mechanism and associated parts;

Figure 5 is an enlarged front elevation of the dimpling dies and associated equipment showing the dies and punch in an actuated condition, the dies appearing in vertical cross section;

Figure 6 is a fragmentary view illustrating the rear side of the heating mechanism and associated parts;

Figure 7 is a horizontal sectional view taken substantially as indicated by line 7-7 on Figure 2;

Figure 8 is a fragmentary vertical sectional view taken as indicated by line 8-8 on Figure 3 showing the heater expanding wedge or cam in the raised position;

Figure 9 is a view similar to Figure 8 showing the cam in the actuated position;

Figure 10 is a reduced horizontal sectional view with certain parts appearing in elevation illustrating the shoe shifting mechanism;

Figure 11 is a view taken substantially as indicated by line 1111 on Figure 10 showing the heating means and other parts in elevation; and

Figure 12 is a combined schematic wiring diagram and flow diagram of the principal circuits and fluid pressure actuating means of the invention.

The hot dimpling means of the present invention is shown herein incorporated in the automatic dimpling, punching and riveting machine illustrated and described in detail in the W. E. Harness 'et al. Patent No. 2,620,876, issued December 9, 1952. For convenience the same reference numerals will be used herein, so far as practical, in designating parts corresponding or analagous to parts so designated in the patent to facilitate reference to the patent.

The machine includes a generally C-shaped frame 10 having a base 11, a lower jaw 12 and an upper jaw 13. The jaws 12 and 13 extend forwardly and are hollow to contain certain of the working parts. An upwardly extending tubular boss 14 is provided on the lower jaw 12 adjacent its forward end to receive the lower anvil, die, and punch, and other elements described below. The active Work engaging elements carried on the lower jaw 13 include a lower die and anvil carrier 15 guided for vertical movement in the tubular boss 14 and provided with a tapered upper portion, see Figure 2. A socket 16 is provided in the upper end of the carrier 15 and receives the shank of a die 17, the upper end of the die having a cavity or recess 19 complementary with the shape of the dimples to be formed in the workpiece W. The die 17 is tubular, having a central vertical opening which slidably receives a rod-like punch 20. The punch 20 in addition to being operable to punch openings in the workpiece is utilized in a later stage of the operating cycle to upset the rivet. A yoke-like member is slidable on the exterior of the die 17 and has a raised surface 91 adapted to engage the underside of the workpiece W in the area immediately surrounding the die 17. The yoke member $4 replaces the tubular stripper 21 of the abovementioned patent. The carrier 15, the punch 25) and the member 99 are each independently operated vertically .by appropriate power devices, for example, cylinder and piston means.

The means for operating the carrier includes a cylinder 23, apiston 2.4 operable in the cylinder and a toggle linkage 26 connected between the piston rod and the carrier. This structure is illustrated in Figure Lines 27 for carrying the actuating air under pressure extend from the opposite ends of the cylinder 23 to a fourway solenoid valve 28 within the jaw 12 The meansfor operating the punch ZQ-includes a cylinder 29 at the. outer end of the arm 12 having a piston rod 311extending from its lower end. A pivoted lever adjacent the lower end of the cylinder 25!, has one end engaged by'the piston rod 31 and has its other end acting inwardly against a rod 33' guided in the carrier 15. An intermediate pushrod 36, seen in Figure 2, is slidabie in the carrier 15 and die 17 and a spring 37 is arranged under compression between the upper end of the rod 33 and an enlargement on the rod 36 to yieldingly support the punch 20 for downward retraction. The weight of the workpiece W is sufiicierit to compress the spring 37 and move the punch 20 downwardly. However, when the piston rod 31 is actuated downwardly, the rod 33 is actuated upwardly to compress the spring 37 until the upper end of the rod 33 engages the lower end of the rod 36 to positively move the punch 20 upwardly to form an opening in the workpiece W. Flexible lines 49 and .40? deliver actuating pressure to the opposite ends of the a solenoid valve 400.

The active assembly carried by the upper jaw 13 includes a dimpling shoe 47 and a riveting shoe 4%, the shoe 47 having an oifset arm 49 and being provided at its lower end with a removable male dimpling die 5%. The riveting shoe 48 has. a sloping arm 51 and is provided at its lower end with a verticaluopening 52. The shoes 47 and 48 are mounted for individual vertical movement and for simultaneous horizontal shifting. Shafts 54 are slidable in spaced vertical openings 53 in the jaw 13, the arm 49 of the shoe 47 being fined to the lower end of one shaft 54 and thearm 51 of the shoe 48 being secured to the lower end of the other shaft. Spring means serves to urge the shafts 54 to upper positions where the shoes 47 and 48 are spaced clear of the work W and to return the parts to these positions after the several operations. Stems 56 extend through the tubular shafts 54 and are provided at their upper ends with nuts 57 engaging the top-surface of the jaw 13. Springs 58 are arranged under compression between the lower heads of the stems 5:; and internal shoulders 59 formed in the upper parts of the shafts. Figure 11 best illustrates this construction.

The means for shifting the shoes 47 and 48 between inactive positions and positions where they are respectively in vertical alignment withthe die 17 includes lever arms tihaving sliding spL ne connections with the shafts 54 so as to allow independent vertical shifting of the shafts while remaining in rotation'transmitting connection with the shafts. The outer ends of thearms 69 are pivotaliy connected with a link 62 housed in the jaw 13, see Figure l0. Cylinders 63 and 64 are secured on the sides of the jaw 13 and have pistons 65 provided with rods as engaging or connected with a lug 67 on the link 62.

ost a i a i P es ur i e 63.6 mass communicate.

with the outer ends of the cylinders 63 and 64 respec tively and are controlled by a solenoid valve 174. The parts are related so that the introduction of air under pressure to the cylinder 63 moves the riveting shoe 43 V to the active position in alignment with the die. 17 while the introduction of actuating'air pressure to the cylinder 64 moves the dimpling shoe 47 to the active position in V Shifting of one shoe to the end of the jaw 13 and a piston-7i operable in the-cylinder. V

The piston 79 has a rod 71 whose lower end carries the ram 53.

to move downwardly through the riveting shoe 48 when the latter is in its active position to drive the rivet. In this latter operation the shank of the rivet is upset against the top of the punch 2i and the female die 17.

' Referring again to the main cylinder 69, it willbe seen in Figure 1 that a reduced stem 75 extends upwardly from the piston 76 and slidably passes through an opening in the head of the cylinder. upper end of the stem 75 and a spring 77 is engaged under compression between the cylinder head and the washer to return the piston 7t and the ram 63 to the raised position when air pressure is released from the cylinder. A suitable cap 7 S on the upper end of the cylinder 6? houses the projecting stem 75, disc 75 and spring 77.

The rivet feeding mechanism for depositing rivets in the rivet shoe 48 when the latter is in the retracted position is omitted from the present disclosure but is described in full in the above referred to patent.

Figure 5 of the drawings illustrates the punch29 in its fully actuated position after it hasformed an opening in' the previously formed dimple in the work W, the punch extending upwardly into an opening 10% in the male dimpling die Stl. The workpiece W is securely clamped between the dies 17 and 50 during the punching operation and the punch 29 is operated upwardly to form the opening in the dimpled work. Prior to each riveting operation a rivet is supplied to the shoe 48 to be: re

tained therein while the shoe is shifted into alignment with the main ram 68. The rivet is subsequently forced into the opening in the dimple anddriven or upset by the action of the main ram 68 and punch 20.

V The construction'thus, far described'is more fully disclosed in the patent referred to above. As described in the patent, the machine is operable to perform the following sequence of operations: (1) dimple the work W;

(2) punch an opening in the dimple (3) insert a rivet in the rivets. The complete sequence and the sub-sequences are interposed in the system betweenthe stages 'B and C.

These additional stages 31, B2 and B3 may each be the same as any of the intermediate stages B, C, D, etc. already described in the patent and, therefore, will not be disclosed in etail here although the circuits and devices controlled thereby will be described below.

The means or apparatus of thei'nvention for heating The ram 63 is engageable with the dimpling die 5' to drive the same downwardly against the work W when the shoe 47 is in theactive position and is adapted.

A washer 76 is secured on the the immediate region of the work W, that is to be subsequently dimpled by the above described mechanism, includes two or more electrical heating elements 94 housed and electrically insulated in the arms of the yoke member 90 to extend to adjacent the raised surface 91. As above described, the member 90 is movable vertically on the anvil 17 so that its stripping and heating face 91 may be moved into and out of pressure contact with the under surface of the work W. The member 90 is preferably constructed of copper or other material that is efficient in the transmission of heat. The heater elements 94 are connected in a circuit 402 which, in turn, is connected with lines 197 extending to a suitable power supply 122. The portions of the circuit 402 adjacent the member 90 are flexible to permit free movement of the member. A manually operable switch 403 is provided in the circuit 402 to permit deenergization of the heaters at will.

The heating means of the invention further includes two members 404 associated with the dimpling shoe 47 to be movable therewith and to be movable with respect thereto. The offset arm 49 of the shoe 47 has a vertically thickened portion 405 provided with a vertical opening 406 lined with a bushing 407 having a low coefficient of thermal expansion and contraction and resistant to relatively high temperatures. A stem 408 is slidable and turnable in the bushing 407 and extends downwardly from the lower side of the arm 49. This is clearly shown in Figure 2. A head 409 is provided on the lower end of the stem 407 and one of the members 404 is welded or brazed thereto. It may be preferred to construct the members 404 of copper or other material that is eflicient in the conduction of heat. The other member 404 has an opening 410 rotatably receiving the stem 408, the two members 404 resting one upon the other in crossed relation for relative pivotal movement and being supported by the head 409 of the stem. A spring 411 surrounds the stern 408 and is under compression between the uppermost member 404 and the underside of the arm 49 to yieldingly urge the members downwardly so as to engage the work W. The members 404 are adapted to extend inwardly toward one another to have their outer or forward end regions directly below the male dirnpling die 50, see Figure 3. These active ends of the members 404 have flat surfaces 412 lying in vertical planes and adapted to bear one against the other and have raised surfaces 413 on their undersides for engaging the circular area of the work W that is to be dimpled. These raised surfaces 413 are of limited area and serve to concentrate the transmission of heat from the members 404 to the particular region of the work W to be subsequently dimpled. Arms 414 project rearwardly from the members 404 and a tensile spring 415 is connected between these arms to urge the members 404 to positions where their surfaces 412 bear one against the other so that the raised surfaces 413 are substantially coincident with the die 50.

The above described pivoted members 404 associated with the dimpling shoe 47 serve to carry electrical heating elements 416. The elements 416 are set or secured in angular arms 417 of the members 404 and extend therethrough to have their ends in or immediately adjacent the forward extremities of the members so as to effectively heat the regions thereof carrying the raised work contacting surfaces 413. The electrical heating elements 416 are, of course, suitably electrically insulated from the members 404. Leads 418 connect the heating elements 416 in the circuit 402, see Figure 12, and have flexible portions at the members 404 to permit free movement thereof.

The invention further provides means for operating the members 404 to retracted positions following the heating cycle to permit free actuation of the dirnpling die 59. This means serves to pivot the two members 404 from their active positions shown in full lines in Figure 3 to the open or inactive positions shown in broken lines in the same figure. The retracting means is preferably fluid pressure actuated and is associated with the dirnpling shoe 47 to move therewith and therefore to move with the members 404. It includes a vertically disposed cylinder 420 secured to the arm 49. In practice the cylinder 420 may be mounted on a horizontal flange 421 projecting from the arm. A piston 422 operates in the cylinder 420 and has a rod 423 extending from the underside of the flange 421. The extending lower end of the piston rod 423 carries a generally conical wedge or cam 424 having its apex facing downwardly. The wedge or cam 424 cooperates with inclined faces 425 on the abovementioned rear arms 414 of the members 404. The faces 425 extend generally in the radial direction relative to the stem 408 and slope downwardly and inwardly or toward one another. The above described spring 415 urges the crossed pivoted members 404 to positions where the arms 414 are adjacent one another, as seen in Figure 8, in which positions the vertical faces 412 at the forward ends of the members are in contact. It will be seen that when the piston 422 is actuated downwardly by fluid under pressure, the cam 424 moves downwardly and cooperates with the faces 425 to spread the rear arms 414 apart and thus move the surfaces 412 away from one another. Figure 9 shows the wedge or cam 424 cooperating with the faces 425 to spread or open the members 404 and the broken lines in Figure 3 illustrate the spread or open positions of the members. It will be seen that when the members 404 are in this open position the faces 412 are spaced apart a sufiicient distance to allow the male dirnpling die 50 to move downwardly between them without interference.

A line or pipe 426 carrying air under pressure for actuating the piston 422 communicates with the upper end of the cylinder 420 and extends from a solenoid operated valve 427. The lower end of the cylinder 420 is vented to the atmosphere by a port 428. The piston 422 and the wedge or cam 424 are actuated downwardly by air under pressure admitted to the cylinder 420 by the valve 427 and a spring 429 is provided to return the piston and cam when the air pressure is released from the upper end of the cylinder. The spring 429 is engaged between the underside of the piston 422 and the lower end of the cylinder. 420 and is operable to normally hold the wedge or cam 424 in the raised retracted position of Figure 8. Although the cam 424 is operable to pivot the members 404 to positions where the dirnpling die 50 may be moved downwardly between the surfaces 412 without interference I prefer to provide sloping faces 430 at the upper corners of the surfaces 412 engageable by the periphery of the die 50 to positively swing the members 404 clear of the die if for any reason the members are not already swung clear when the die descends. The faces 430 are best shown in Figure 5.

Figure 12 illustrates the electrical diagram and the actuating fluid pressure controls of the machine insofar as the present improvement is concerned and the operation of the apparatus will be described in connection therewith, reference being bad to the corresponding designated control circuit elements, etc. of the above identified patent. To condition the machine for operation, switch 159 connected in the power line and connected in series with the foot switch 154, relay 103 and safety switch 155 is closed. With the switches 155 and 159 already closed, foot switch 154 is manually actuated or closed to apply D. C. current to all stages, A to H inclusive of the electronic control and this initiates operation of the machine. Stage A is connected with relay 171 by line so that upon actuation of stage A relay 171 is energized to operate or reverse solenoid valve 174. The valve 174 connects the air pressure supply manifold 175 with pipe 690 leading to one of the shifting cylinders 54 and the air pressure supplied to the cylinder actuates the piston 65 therein to move the dirnpling shoe 47 into alignment with the main ram 68. When the shoes 47 and 48 are shifted in this manner the piston 65 in the other cylinder 64 is moved into engagement with a contact 166 connected in amass-r a circuit 155 leading to terminal 1 of electronic stage, B. Engagement of the .piston 65 with contact 166 fires or energizes stage B. V

Electronic stage B in turn suppliescurrent to wire to energize relay 17 7. Relay 177 energizes solenoid valve 130 which connects the air. pressure supply manifold 175 with a pipe 1% leading to the upper end of the main cylinder 69. A pressure switch 432 responsive to the air pressure in pipe. 1913 controls an electrically actuated valve 433 to limit the pressure exerted on the main piston Mat this time. The pressure switch 432 may be of the diaphragm type and may be adjusted to admit air to the main cylinder 69 at about p; s. i. This air under pressure forcesthe piston 70 and main ram efirdownwardly to, in turn, press the heater members 494 downwardly against the work W. The heating elements 416, as well as the heating elements 94, are supplied with current by the circuit 492 and the members 464 as well as the stripper or memberSt are hot when the work W is thus clamped between the surfaces 433 and 91. it should be observed that the surfaces 413 and 9ltransmit the heat directly to the area of the workpiece or pieces VJ that is to be subsequently and immediately dimpled. Further, it should be noted that the work W is confined under pressure between the heating surfaces 91 and 413 for the most efiicient conduction ofuhcat to the area to be dimpled. Electronic control stage 3 may be set or adjusted to cause heating of the area to be dimpled for any selected time, for example 1 /2 seconds. When stage B has timed out stage B1 is automatically fired or energized and stage B1 supplies current to a circuit 435 which energizes relay' 436. Relay 436 has a contactor 437 in the circuit 196 of solenoid valve 15 3 and when relay 436 is energized upon actuation of electronic stage Bl this contactor 437 opensto deenergize or reverse solenoid valve 193. This exhausts air under pressure from the main cylinder 69 and the spring 77 returns the main ram 68 upwardly.

Thus downward pressure is removed from the heater jaws or members 494. Stage B1 is adjusted or set to allow just sufiicient time for the downward pressure to be released from the heater members4tl4 and thereupon fires or triggers stage B2.

Nhen electronic stage B2 thus becomes active it supplies current to a circuit 438 leading to a relay 440. Relay 449 when energized connects solenoid valve 427 with the power line 197 and valve 427 in turn connects a pipe 426 with the air pressure supply manifold 175. Pipe 426 leads to the cylinder 42 so that upon actuation of solenoid valve 427 actuating air under pressure is admitted to the cylinder 420 to actuate thewedge 424 downwardly The wedge or cam 424 spreads or pivots the heater jaws 404 to their open positions. The invention includes a micro-switch or equivalent switch 441 attached to the offset arm 49 of the dimpling shoe to move with the dimpling shoe. A post 442 projects from one of the angular arms 417 to engage and actuate the lever or arm 443 of the micro-switch 441 when the heater jaws 494 reach their fully open positions. The switch 441 is connected in a grounding circuit 444 of electronic stage B3. When switch 441 is closed stage B3 is triggered or energized.

Electronic stage B3 supplies current to a line or circuit 445 to energiz relay 177. Relay 177 in turn operates solenoid valve 189 to supply actuating air under pressure to the main cylinder 69 to actuate the. main ram 68 downwardly. It is to be observed that at this time the heater members 404 are open or spread apart to allow the dimpling die-5tl to directly contact the heated area of the work W to dimple the same into the female die cavity 19. A relay 447 supplied with current from terminal 3 of stage B3 by line 448 serves to deenergize the pressure controlling valve 433 to allow full actuating air pressure to be applied to the main cylinder 69 for the dimpling operation. While the present. invention is'not primarily concerned with the details of the control system 'it may be noted that a gang switch designated Hot-Cold in Figure 12 has contactors 450', 451, 452 and 453 operable when opened to disconnect electronic stages B1, B2 and BSfrom the system so that the machine may be operated through the desired cycle without heating the work and a relay 434 serves to open circuit 438 so as to disconnect relay 44% and solenoid valve 427 from the system for the .same reason. Following the dimpling operation the main ram 68 is raised, the riveting shoe 48 is moved into alignment with the main ram, a

rivet is inserted and the rivet is then driven, all as de- 1 scribed in the above. identified patent.

Having described. only typical forms of the invention carried by the shoe, the combination of a first heating means carried by the anvil to surround the first die to contact the lower surfac of the workpiece to be dimpled,

. a second heating means movably carried by the shoe to be interposed between said second die and the upper surface. of the workpiece and to be pressed against said upper surface by the ram, the second heating means being retractable out of alignment with the dies, and means. for retracting said second heating means clear of the dies when'ram pressure is released to clear the dies for the dimpling operation. 7 l

2. In a dimpling machine including an anvil upon which a workpiece rests and carrying a first dimpling die, a ram movable toward and away from the first die, a. shoe between the ramand anvil yieldingly supported to be moved toward the anvil by the ram and to retract away from the anvil upon return of the ram and a second die carried by the shoe; the machine being characterized by a first heating means on the anvil to contact the lower surface of the workpiece to be dimpled, a second heating means, means mounting the second heating means on the shoe for movement thereon between an active position between said second die and the upper surface of' the workpiece tobe pressed against said upper surface by the action 'of'the ram on said second die and a retracted position out of the path of movement of said second die, and means for moving said second heating means to the retracted position when ram pressure is released to clear said second die for the dimpling opera-tion.

3 In a dimpling machine including an anvil for supporting aworkpiec and carrying .a first dimpling die, a ram movable toward and away'from the first die, a shoe between the ram and anvil yieldingly supported to be moved toward the anvil by the ram and to r tract away from the anvil upon return of the ram and a second die carried by the shoe to contact a substantially circular area of the upper-surface of th workpiece; the machine being characterized by a first heating means on the anvil to contact the lower surface of the workpiece area to be dimpled', asecond heating means, means mounting the 7 is released to move said second heating means to said retracted position.

4. In a dimpling machine including an anvil carrying a first dimpling die, a ram movable toward and away from the first die, a shoe between the ram and anvil yieldingly supported to be moved toward the anvil by the ram and to retract away from the anvil upon return of the ram and a second die carried by the shoe; the combination of a first heating means on the anvil to contact th lower surface of the workpiece to be dimpled, a second heating means including a member pivoted on the shoe for movement between an active position between the upper surface of the workpiece and said second die to be pressed against said upper surface by the action of the ram on said second die and a retracted position out of the path of movement of said second die, and means for moving said member to the retracted position when the ram pressure is released.

5. In a dimpling machine including an anvil carrying a first dimpling die, a ram movable toward and away from the first die, a shoe between the ram and anvil supported to be moved toward the anvil by the ram and to retract away from the anvil upon return of the ram and a second die carried by the shoe; the combination of a first heating means on the anvil to contact the lower surface of the workpiece to be dimpled, a second heating means including a pair of heating jaws pivoted on the shoe for movement between active positions where they are be tween said die and the upper surface of the workpiece to be pressed against said upper surface by the action of the ram on said second die and retracted positions out of the path of movement of said second die, and means for moving the jaws to the retracted positions when the ram pressure is removed from said second die.

6. In a dimpling machine including an anvil carrying a first dimpling die, a ram movable toward and away from the first die, a shoe between the ram and anvil yieldingly supported to be moved toward the anvil by the ram and to retract away from the anvil upon return of the ram and a second die carried by the shoe; the combination of a first heating means on the anvil to contact the lower surface of the workpiece to be dimpled, a second heating means, a member carrying the second heating means, means mounting the member on the shoe for movement between an active position where the second heating means is substantially aligned with the first die to contact the lower surface of the workpiece and a retracted position where the second heating means is out of alignment with the first die, and a cylinder and piston means on the shoe for moving said member to the retracted position when the ram pressure is released from the shoe.

7. In a dimpling machine including an anvil carrying a first dimpling die, a ram movable toward and away from the first die, a shoe between the ram and anvil yieldingly supported to be moved toward the anvil by the ram and to retract away from the anvil upon return of the ram and a second die carried by the shoe; the combination of a first heating means on the anvil to contact the lower surface of the workpiece to be dimpled, a second heating means including a pair of heating jaws pivoted on the shoe for movement between active positions when they are between said die and the upper surface of the workpiece to be pressed against said upper surface by the action of the ram on said second die and retracted positions out of the path of movement of said second die, and cylinder and piston means on the shoe for moving the jaws to the retracted positions when the ram pressure is removed from said second die.

8. In a dimpling machine including an anvil for supporting a workpiece carrying a first dimpling die, a ram movable toward and away from the first die, a shoe between the ram and anvil yieldingly supported to be moved toward the anvil by the ram and to retract away from the anvil upon return of the ram and a second die carried by the shoe for acting on a substantially circular region of the upper surface of the workpiece; the combination of a first heating means on the anvil to contact the lower surface of the workpiece to be dimpled, a second heating means including a pair of heating jaws pivoted on the shoe for movement between active positions where they are between said die and the upper surface of the workpiece to be pressed against said upper surface by the action of the ram on said second die and retracted positions out of the path of movement of said second die, said jaws including protruding heat transmitting areas of limited extent for pressing against the substantially circular region of the workpiece that is to be engaged by said second die, and means for moving the jaws to the retracted positions when the ram pressure is removed from said second die.

9. In combination with a dimpling machine having an anvil and a dimpling shoe movable one toward the other, dies on the anvil and shoe to contact the opposite surfaces of the workpiece to dimple an area thereof, means for preheating the area of the workpiece to be dimpled while in position between the anvil and shoe comprising a first heating member carried by the anvil to contact one side of the workpiece immediately adjacent the area to be dimpled, a second heater member carried by the shoe for movement between a retracted position clear of said area and a second position to contact the other side of the workpiece at the area to be dimpled, means for operating the shoe and anvil one toward the other when said second heater member is in said second position to clamp the workpiece between the first and second heater members, and means for retracting the second heater member to the retracted position for the dimpling operation.

10. In combination with a dimpling machine having an anvil and a dimpling shoe movable one toward the other; dies on the anvil and shoe to contact the opposite surfaces of the workpiece to dimple an area thereof, means for preheating the area of the workpiece to be dimpled while in position between the anvil and shoe comprising a first heating member carried by the anvil to contact one side of the workpiece immediately around the area to be dimpled, a second heater member carried by the shoe for movement between a retracted position clear of said area and a second position to contact the other side of the workpiece at said area to be dimpled, electrical heater elements in the two members, means for operating the shoe and anvil one toward the other when the second heater member is in said second position to clamp the workpiece between the first and second heater members, and means for retracting the second heater member to the retracted position for the dimpling operation.

11. In combination with a dimpling machine having an anvil and a dimpling shoe movable one toward the other to contact the opposite surfaces of the workpiece to be dimpled; male and female dies on the anvil and shoe for dimpling the workpiece, means for preheating the area of the workpiece to be dimpled while in position between the anvil and shoe comprising a first heating member carried by the anvil having a protruding surface to contact one side of the workpiece immediately around the area to be dimpled by said dies, a second heater member carried by the shoe for movement between a retracted position out of alignment with said dies and a second position in alignment with the dies, the second member having a protruding surface region operable when in the second position to contact the other side of the workpiece at the area to be dimpled, means for operating the shoe and anvil one toward the other when said second heater member is in said second position to clamp the workpiece between the first and second heater members, and means for retracting the second heater member to the retracted position for the dimpling operation.

12. In combination with a dimpling machine having an anvil and a dimpling shoe movable one toward the other; dimpling dies or the anvil and shoe to contact the opposite surfaces of the workpiece to dimple an area of the work piece, means for preheating the area of the workpiece to be dimpled while in position between the anvil and shoe comprising a first heating member carried by the anvil to 11 V cqntact'one side of, the workpiece immediately aroundgthe area to' be dimpled, a pair of second heater members pivoted to the shoe formovement between retracted positions clear oi the dies and active positions where they contactthe other side'of the workpiece at the area'to be dimpled, means for eifectingrelative movement between the shoe and anvil when the second heater members are in the active'positions to, clamp the workpiece between the first and second heater members and to then free the shoe from the workpiece, and means for movingthe second heater members to the retracted positions for the dimpling'operations'. 1 V

13. In combination with a dimpling machine having an anvil and-a dimplingshoe movable oneto ward the other; dimpling dieson the anvil and shoe to contact the opposite surfaces of the workpiece to dimple an area of the workpiece, means for preheating the area of the workpiece to be dimpled while. in positionbetween the anvil and shoe comprising a, first heating member carried by the anvil. to contact one side of the workpiece immediately adjacent the area to be .dimpled, a pair of second heater members pivotedtothe shoe for movement between retracted positions clear of. the dies and active positions .where they contact the other side of the workpiece at the area to be dimpled, means for efiecting relative movement between the shoe and anvilv when the second heater members are in said active positions to clamp the workpiece between the first and second heater members and to then free 12 the, shoe from, the workpiece, and means for movingjhe second. heater members to said retracted positions clear. of the dies for the dimpling operations including aicam; for moving between the members, and cylinder means on: the shoe for actuating the cam.

14. In a dimpling machine having an anvil upon which the'workpiece rests the combination of; a die on the anvil,

a shoe movable toward and away from the workpiece and V carrying a dimpling die, ram means for moving the shoe toward the anvil and workpiece, a heater member carried by the shoe for movementtherewithand for movement;

with respect thereto between an initial active position between the die of the shoe and theworkpiece to be pressed against the workpiece at thearea to be dimpled bythe. action of the ram means which movesthe shoe toward the workpiece and a retracted position clear of thedies, and means on the shoe for moving themember tothe retracted position when the pressure of the ram means is released. i i

' References Cited in thefile'of this patent i V UNITED STATES PATENTS 

